The sentence for anyone convicted of misdemeanor or felony DWI must include installing an ignition interlock.

What cars must they go on?

Any vehicles owned or operated by the offender. That includes borrowed, rented or leased vehicles. A company car owned by the offender’s employer is exempt, but the offender must notify the employer, must prove the employer will allow the offender to drive the vehicle, and can use it only for business. A self-employed offender must install an interlock on his work vehicles. A judge may allow an offender to transfer ownership of a vehicle to a spouse, but still must drive a vehicle with an interlock; failure to do so is a misdemeanor punishable by a year in jail.

How much do they cost?

¦It depends on the manufacturer and features. Installation runs from no charge to $125. Basic monthly fees range from $69.50 to $90. Companies may also charge reset fees, insurance cost, road service charges and more.

How long must it stay on?

At least six months and up to three years for a misdemeanor offender, or up to five years for a felony offender.

Who pays?

The offender pays for installation and maintenance. Under the state contracts, if a judge using Office of Probation guidelines decides that the offender is unable to bear the cost, the manufacturer is required to pick up the bill. No taxpayers would bear the increase.

How do they work?

The ignition interlock includes a mouthpiece attached to a computer that is wired into the ignition. The offender must blow into the mouthpiece to start the vehicle. After the car is running, the car horn will sound and the interlock will emit a shrill tone at random intervals, telling the operator to pull over, shut off the engine and restart it. A blood-alcohol content of 0.025, the equivalent of one drink, will prevent the car from running.

Can anything other than alcohol trigger it?

It’s possible for yeast from pizza dough or alcohol from mouthwash or hand sanitizer to cause a false positive. The interlock will give the operator time to clean up and try again, but repeated failures will cause a lockout. In that event, the offender has five days to bring the car to a service center to be reset. If he or she doesn’t, the car won’t work on the sixth day and the incident is reported to authorities.

Can it be fooled?

Offenders can’t fool the machine by washing out their mouths because the interlock samples deep lung air.
Nor can they fool it by having a sober person blow — most interlocks have cameras that record who is at the mouthpiece and it is a misdemeanor to blow into it for someone else. Also, within five minutes the interlock will order the driver to pull over and restart the car.

Who else does this?

According to the Insurance Institute for Highway Safety, the other states that require all DWI offenders to install interlocks are Alaska, Arizona, Arkansas, Colorado, Illinois, Louisiana, Nebraska, New Mexico, Oregon, Utah and Washington. Hawaii is to join them Jan. 1. Nine other states require them for all repeat offenders and first-timers who registered high blood-alcohol contents.